Triflin Explained

Triflin is a cysteine-rich secretory protein (CRISP), which is excreted by the venom gland of the Habu snake (Trimeresurus flavoviridis).^[1] Triflin reduces high potassium-induced smooth muscle contraction, suggesting a blocking effect on L-type calcium channels.^[2]

Sources

Triflin is a toxin derived from snake venom. The toxin is produced in the gland of the Habu snake, Trimeresurus flavoviridis.^[1]

Chemistry

Triflin is a cysteine-rich secretory protein, which means it belongs to the CRISP family. This is a group of single chain polypeptides found in various organisms.Triflin weighs 25 kDa and consists of 221 amino-acid residues. The first 163 residues of the N-terminal domain forms an α-β-α sandwich core. This domain is comparable with group 1 plant pathogenesis-related protein (PR-1).The C-terminal domain, has five disulfide bridges. This domain is responsible for the selectivity of the protein and consists of two subdomains: N-terminal subdomain (Cys 167 to Cys 179) and C-terminal subdomain (42 amino-acids residues).The N-terminal subdomain is connected with N-terminal domain through two main-chain hydrogen bonds between β11 and β2 and is thereby part of the PR-1 domain. The C-terminal subdomain is stabilized by three disulfide bridges and it is remarkable that this domain does not interact with either the PR-1 domain or the N-terminal sub-domain. The C-terminal subdomain consists of particles, including some hydrophobic residues that are exposed to the solvent. These hydrophobic residues might mediate the interaction with the target proteins and therefore receptor recognition.^[1]

There are some homologous toxins to Triflin with different percentages of amino-acid sequence similarity, such as Ablomin, Latisemin, Stecrip (88%), Helothermine (49%),^[2] Pseudechetoxin (62%), Pseudesin (61%).^[3] The snake venoms which belong to CRISP family seem to be homologous to each other, however there are differences in their protein targets.^[1]

Target

Triflin reduces high potassium induced smooth muscle contraction, suggesting a blocking effect on L-type calcium channels.^[2]

Treatment

One of the small serum proteins (SSP-2), a substance produced by Trimeresurus flavoviridis itself, has high affinity for Triflin, and may thus work as a defensive mechanism against accidental self-poisoning, suggesting a possible role for SSP-2 as an antidote to triflin.^[4]

See also

• Other snake venom proteins in the CRISP family:
  • Piscivorin from the Eastern Cottonmouth
  • Latisemin from the Erabu snake
  • Ablomin from the Mamushi snake
  • Ophanin from the King Cobra

Notes and References

1. 10.1016/j.jmb.2005.05.020 . Y, Shikamoto . Suto . 2005 . K . Yamazaki . Y . Morita . T . Mizuno . H. Crystal structure of a CRISP family calcium-channel blocker derived from snake venom. Journal of Molecular Biology. 350 . 4. 735–743 . 15953617.
2. Y. Yamasaki . 2002 . Koike . H . Sugiyama . Y . Motoyoshi . K . Wada . T . Hishinuma . S . Mita . M . Morita . T . Cloning and characterization of novel snake venom proteins that block smooth muscle contraction. Eur. J. Biochem. . 269 . 11. 2708–2715. 12047379 . 10.1046/j.1432-1033.2002.02940.x. free .
3. N, Suzuki . 2005 . Yamazaki . Y . Fujimoto . Z . Morita . T . Mizuno . H . Crystallization and preliminary X-ray diffraction analyses of pseudechetoxin and pseudecin, two snake-venom cysteine-rich secretory proteins that target cyclic nucleotide-gated ion channels. Acta Crystallogr F . 61 . Pt 8. 750–752. 16511147 . 1952345 . 10.1107/S1744309105020439.
4. Aoki . N . Sakiyama . A . Deshimaru . M . Terada . S . Identification of novel serum proteins in a Japanese viper: homologs of mammalian PSP94 . Biochemical and Biophysical Research Communications . 359 . 2 . 330–4 . 2007 . 17543280 . 10.1016/j.bbrc.2007.05.091.